1. Field of the Invention
The present invention relates generally to a method for recovery by flocculation of fats, oils, grease and/or proteins from a waste stream and to a method of using the recovered solid material (sludge) in animal feeds, as a fuel source or as a fertilizer.
2. Description of the Related Art
U.S. Pat. No. 4,548,615 relates to a process for manufacturing a solid fuel composition by admixing vegetable organic material with an oil-in-water macro-emulsion and drying the resultant composition. The oil of the emulsion is a hydrocarbon oil with oil droplets ranging from 0.5 to 20 micrometers. The resultant mixture is put in shape and dried. Emulsification of the hydrocarbon can be effected by passing a mixture of hydrocarbon, oil and an emulsifier through a suitable mixer. The heavy hydrocarbon oils used include any oil or coal derivative with an appropriate viscosity. The organic materials may originate from waste materials, cultivated energy-producing plants or natural fields. The waste materials include that from human or animal origin including combustible residues from the food-agriculture industry.
U.S. Pat. No. 4,744,903 relates to a process for facilitating the separation of fat from a waste stream composition comprising water, fat, fatty acids and solids produced in food processing plants and animal rendering plants. An alkaline pH control composition and an aluminum salt flocculent composition are added to the waste stream composition for subsequent separation in a clarifier of the waste stream composition into an essentially fatty layer, an essentially water layer, and an essentially solids layer. The pH control composition is a combination of a compound or a mixture of compounds. A flocculent composition, such as aluminum sulphate, alone or in combination with an enzyme such as protease, may also be used. These compositions are added to the waste water stream containing solids and inedible fats in amounts which are effective to provide an increase in fat separation from the waste stream. The skimming of the top layer of fat for selling as inedible tallow is contemplated.
U.S. Pat. No. 4,828,577 relates to a process for treating feed waste water from a food preparation plant to recover substantially all of its fats and up to fifty percent of its proteins in a chemical float sludge which is then selectively admixed with an absorptive bulking agent, such as sawdust. The resulting biomass mixture is dried to produce a biomass fuel for self-sustaining burning in a gasifier-type suspension burner. The admixing of a flocculation chemical, a solution of a coagulation chemical, and a stream of compressed air into the waste water stream are contemplated.
U.S. Pat. No. 4,906,386 relates to a flocculation of coal fines from an aqueous suspension by adding an anionic polyelectrolyte, a soluble calcium salt, and a cationic polyelectrolyte to the suspension.
U.S. Pat. No. 4,933,087 relates to a process for treating food waste waters by adding a specific composition to assist in coagulation and flocculation of the waste water. Sludges produced from the process are used in foods suitable for animal consumption.
U.S. Pat. No. 4,966,713 relates to a process for treating waste containing effluent water from a food processing plant. The effluent water is contacted with a flocculent comprising a crude algal composition or a crude alkali processed algal composition at an acidic pH. A floc containing substantially all of the solid waste components of the effluent water is formed as a result of the treatment process. The resultant floc can be recovered and used in animal feed stocks or in other products, such as fertilizers, or is disposed of in a landfill operation.
U.S. Pat. No. 5,015,391 relates to a method for treating emulsified oil contaminants in the waste water effluent of industrial and food processing operations. Cationic polymers and silicate ions coagulate oily particles in the waste water to facilitate removal from the water.
Limits on industrial process wastewater that is discharged into municipal sewage systems and sanitary districts are being imposed and fines levied against producers of industrial waste for exceeding the limits. Limits are placed on fats, oils and greases (FOG), biological oxygen demand (BOD), chemical oxygen demand (COD), and suspended solids (SS) in the waste stream. It is, therefore, important that the amounts of contaminants in the waste water emitted from a processing plant be controlled.